1. Field of the Invention
The present invention relates to a telescopic jib bearing assembly including at least two telescopic parts, hollow in cross-section, for a telescopic jib correspondingly configured, and a mobile crane having such a telescopic jib bearing assembly.
2. Description of the Prior Art
Telescopic jibs, for example those of fixed or mobile cranes, are made up of several telescoping parts which can be extended for lengthening the jib. The telescopic parts particularly in the case of telescopic cranes are nested such that the inner telescopic part slides on bearing elements in a collar or on the inner wall of the outer telescopic part.
Conventionally optimized jib sections are dimensioned in the overlapping, highly shear-stressed region according to buckling stability criteria. In the case of larger cross-sections either longitudinal strips, transverse strips or localized thicker plates are employed. Additional reinforcements are often necessary in the force application zone between the inner telescopic part and the collar or the outer telescopic part. Side guides are necessary in ensuring the side straightness of the jib as a whole.
Broadly known from U.S. Design Pat. Des. 299,079 and Des. 299,179 are telescopic jibs having embossments and transverse strips, these embossments and transverse strips being distributed on the full length of the telescopic parts.
The telescopic jib bearings as cited above in accordance with related art feature in the force application zone and overlapping portion of two telescopic parts, low stability or can only be rendered stiff to buckling by complicated design. Also the lateral guidance and the orientation of the telescopic parts relative to each other is either deficient or can only be achieved by complicated design.